This invention relates generally to sputtering apparatus using a magnetic field and generally known as planar magnetron apparatus. Magnetron cathodic sputtering is widely known and extensively used for the coating of thin material onto substrates. The process involves the transport of a material from a cathode to a substrate via the vapor phase. The ejection of the material into the vapor phase is accomplished by bombarding the cathode target with ions of sufficient energy to cause atoms or molecules of the target material to be ejected from the target surface. The process is carried out in a chamber that has been substantially evacuated of air and normally contains a small amount of inert gas. The ejected particles traverse the low pressure gaseous space and condense onto the substrate, forming a thin film coating on the surface thereof.
The process of sputtering with magnetron apparatus is relatively well known and is described in U.S. Pat. Nos. 3,878,085, Corbani; 4,025,410, Stewart; 3,956,093, McLeod; and 4,013,532, Cormia et al.
Objectives constantly sought in the development of cathode magnetron sputtering apparatus and processes are increases in the rate of sputtering, i.e. more rapid thin film coating, and eveness in film thickness, i.e. uniformity of coating.
In addition, the application of films to larger substrate areas is a constantly sought after objective. Economical means of coating large areas such as panes of plate glass for large windows has been a subject of interest and need.
The present invention is directed to these objectives by providing apparatus that is capable of being constructed in relatively large configurations and by providing uniformly sputtered film coatings in large planar substrates with especially efficient use of the magnetic field produced by the magnets.
Controlling stray electrons and controlling the erosion pattern in planar magnetron cathode sputtering apparatus is constantly sought after in the construction of these devices. When stray electrons are allowed to pass beyond the area of the substrate and tangentally leave the zone of maximum sputtering intensity, uneven erosion of the target takes place. In addition some sputtering occurs on other portions of the apparatus itself rather than on the substrate, which is also undesirable.
The present invention provides apparatus for better controlling the sputtering zone and for promoting more even erosion of the target area. The apparatus includes a planar magnetron cathode and associated components for sputtering onto two different surfaces simultaneously.